1. Field
The subject invention is in the field of extendable/retractable apparatus such as tent poles, fishing rods and boat hooks which can be set at any length within a length range. More specifically it is in the field of such apparatus which incorporates mechanism by which one mechanism at one end of the apparatus operates and controls another mechanism at the other end of the apparatus. Still more specifically it is in the field of such apparatus and related mechanisms adapted for use with apparatus used in construction of dry walls in buildings, apparatus known in the trade as a flat finishing box, used in the crowning and finishing of taped joints between drywall panels.
2. Prior Art
The closet known prior art is shown in the patents listed below. These patents are: U.S. Pat. Nos. 2,934,937, 3,146,481, 3,105,262, 3,090,984, 4,592,797.
In the field of drywall construction and finishing, apparatus termed a flat finishing box is attached to a handle to enable the operator to apply the box to the joints being serviced by the box. To adapt the apparatus to various use situations various lengths of handles are needed to work with, for example, a variety of heights of ceilings and, also, the box must be set in a range of angles with respect to the long axis of the handle. The conventional apparatus comprises a fixed length handle with a lever at one end operable to lock the box pivoted at the other end of the handle at a specific angle to the handle axis. When a variety of lengths of handles is required, it is necessary either to have a number of flat finishing boxes, each attached to a specific length handle or to use fewer boxes than handle lengths required, (usually one box) and interchange the box or boxes from handle to handle in order to have the box on a handle of suitable length. The use of multiple boxes, each with a different length handle attached, is not generally acceptable because of the cost and because the compound used in the boxes sets up, i.e. hardens, so that compound in boxes not fully emptied in use is wasted and removal of the wasted compound is time consuming. The use of fewer boxes than handles is standard practice but changing the boxes from handle to handle is time consuming and tends to be awkward if the box contains the compound referred to in the trade as "mud".
Therefore, for flat finishing drywall joints more efficiently in terms of the inter-related factors of time and cost, there has been a longstanding need for a flat finishing tool with an adjustable length handle, particularly one adjustable to any length within a length range.
The apparatus shown in U.S. Pat. No. 3,090,984 issued to Dunnigan constitutes an earlier attempt to meet this need. The apparatus is shown in FIG. 1A which is FIG. 5 of Dunnigan's patent. This apparatus is considered to not adequately meet the need for at least two significant reasons. First, it does not resemble the conventional widely used and accepted handle used on flat finishers. The conventional handle is a single tube having the flat finishing box pivotally and lockably attached to one end and an operating lever at the other end, accessible to and usable by the operator of the finisher without significant repositioning of the hand grasping the lever end of the handle. Operating the lever locks the flat finishing box at a specific angle, in a range of angles, to the handle. Second, in the Dunnigan apparatus the operating lever 88, used for adjusting the angle of plate 10 to tubes 62 and 64, is attached to tube 62 so that the distance from lever 88 to part 86 and the related mechanism does not change when the length of the apparatus is adjusted by loosening thumb screws 66 and 68, moving tubes 62 and 64 telescopically in sections 56 and 58 respectively of tube 60 and retightening the thumb screws. This means that the distance of handle 88 from the operator changes each time the length of the apparatus is changed. This fact adds to the difficulty of using the apparatus resulting from not having the lever at the end of the handle. The angle adjustment mechanism does not change length with changes in length of the handle. Accordingly, the primary objective of the subject invention is to provide a handle, adjustable to any length within a length range. Other objectives are that the handle be adjustable quickly and easily, without significant repositioning of the user's hands and that the apparatus be reliable, durable and economical to manufacture.